That's right. However, and I've mentioned this before - you don't need a Derrick Henry. Those are hard to find. But it's not hard to find backs that are big enough to break arm tackles.
One of the problems you have is that your smallish backs aren't breaking the simplest of arm tackles.
I don't see much, but I don't need to in order to be entirely shocked at how easy your backs are to bring down. You'd be surprised at how many chunk plays aren't made because the backs are brought down by the first defender's arm tackle. Miami's backs are only able to get the yardage that is blocked, and there's not much there. It's required to have a back that can get the yardage that isn't blocked by breaking tackles and falling forward - instead of backward.
Furthermore, they can't hold up in pass protection. Miami keeps signing these bigger backs like Jordan Howard and Malcolm Brown because they know their backs are too small. But the situations they bring them in give away to the defense what's about to happen. They keep passing up the quality backs on Day 2 of the draft as if it's not important. Being able to plug in any Day 3 back and not have the running game miss a beat sounds good in theory - but it only works if you're capable of building the offensive line to that spec. Miami is not being honest with themselves about their weaknesses in player evaluation, and the coaches only magnify those weaknesses with their personnel groupings. Everything is forecasted to the opposing defense in terms of their TE and RB personnel groupings.
It's alarming how long Miami goes without having a RB even sniff a 100 yard game since 2019. You could probably even say 50 yards in most games if you get right down to it.
Somebody in Miami has an affinity for small backs, poor offensive lineman, inexperienced coaches, and receivers that enjoy watching the game instead of playing in it.